Hydraulic brake system



July 15, 1941. .1. w. DUDLEY I HYDRAULIC BRAKE SYSTEM Filed Marbh 4, 1941 Patented July 15, 1941 r Jay w. Dudley, Knoxville, Tenn.

Application March 4, 1941, Serial No. 381,732 a 5 Claims. (Cl. 188-152) This invention relates to hydraulic brake systems, particularly for automotive vehicles, although not limited thereto, and has particular reference to improvements in hydraulic brake systerns of the general type in which a master unit is employed to exert force on the liquid in the system to eflect brake-applying actuation of the hydraulically operable brake-applying units of the system.

In hydraulic brake systems of the general type referred to the master unit usually includes a liquid reservoir from which liquid is supplied to the system to maintain the latter filled and into which liquid flows from the system when the brakes are released.

.,Since, ...in most ..brake systems oiethe type-,referred to liquid flows into the liquid reservoir when the brakes are released, it follows that as the brakes wear and are required to bemoved farther from their released positions to. their applied positions, progressively increasing amounts of movement of the foot pedal or equivalent element usually employed for actuating the master unit are required to eilect application of the brakes. The range oi movement of the foot pedal or equivalent element is, however, usually limited and thus it follows that after a certain amount of wear of the brakes has occurred the foot pedal or equivalent element no longer is eilective to impart suillcient movement to the master-piston to effectively apply the brakes. when this condition is reached or approached it becomes necespanying drawing and defined in the appended claims.

In the accompanying-drawing, wherein like characters of reference denote corresponding 1 parts in the 'diilerent views:

Figure 1 is 'a diagrammatic sectional view of a hydraulic brake system embodying the featuresof the invention.

Figure 2 isa central, longitudinal sectionv through the unit, interposed in the system to compensate for wear of the brakes; and

Figure 3 is a cross section on the line 3-3 of Fig. 2. 1

Referring to the drawing in detail, A, A desigsary to adjust the brakes to compensate for wear thereof.

Adjusting brakes periodically to compensate for wear is a nuisance and involves material expense. Accordingly, the object of the present invention, generally speaking is to providejin a hydraulic brake system of the type mentioned, simple. inexpensive, practical. reliable and emcient means to e iminate any necessity of ad- .iusting the brakes or any part of the system to compensate for wear of the brakes-in other words, to provide means whereby the amount of movement of the brake pedal or equivalent element required to apply the brakes remains the same regardless of wear of the brakes.

With the foregoing and other objects in view,

which will become more fully apparent as the nature of the invention is better understood, the same consists in the novel combination and arrangement oi parts and in the novelfeatures of construction thereof, as will be hereinafter more fully described, illustrated in the accomfor spreading said shoes into braking engagement and one of the rear wheel brakes of an automotive vehicle, B designates, generally, a master unit hydraulically connected with the brakes A, A and including an element movable to exert force on liquid in the system to eifect application of the brakes, and C designates, generally, a unit constructed in accordance with a practical embodiment of the invention and interposed in the system between the brakes A, A and the master unit B to render the master unit B'eflective by an unvarylng amount of movement of the movable elemen-t thereof to apply the brakes regardless of wear on the same.

As far as the present invention is concerned the particular form of, the brakes A, A is immaterial, other than that each of the same shall include a hydraulically operable unit to efl'ec't its application and suitable spring means to effect its release. In the present instanceand by way of example the brakes A, A are illustrated as be-' ing of a well known type each comprising a drum III which is understood to be carried by a, related vehicle wheel, shoes II for cooperation with said drum, spring means I2 for effecting release of said shoes, and a hydraulically operable unit l3 with said drum, the unit I 3. comprising a cylinder I4 and a pair of pistons l5, l5 therein respectively associated with the shoes and adapted to bemoved apart by liquid forced therebetween to spread the shoes.

As far as. the present invention is concerned the particular form of the master unit B like-.

wiseis immaterial, other than that it shall include an element movable to force liquid to the units 13 and means i'or'insuring a liquid-filledcondition of the system at all times. In the resent instance the unit B is illustrated as being of -a'known type comprising a cylinder IS. a

piston I! in said cylinder movable in one direction by a foot pedal i-l to exert brake-applying force on the liquid in the system, a pair of springs l3 and 20, one associated with the foot pedal it and the other with the piston 11 for retracting said foot pedal and piston upon release of force from the foot pedal, and a reservoir 2| having communication with the cylinder "by a port 22 located at a point to admit liquid to the system when the piston I 1 is fully retracted to insure a liquid-filled condition of the system at all times.

Leading from the delivery end of the cylinder l3 is a pipe 23 which is connected by branch pipes 24 with the hydraulically operable units l3 ofthe brakes A, said branch pipes being connected in the present instance with the cylinders II I,

between the pistons II, II therein. a

The. unit C is interposed in the pipe 23 preferably adjacent to the cylinder i6 and comprises a housing composed of mating sections 23 and 23 bolted or otherwise suitably fastened together and confining between their marginal portions the marginal portion of a flexible diaphragm 21 which divides the system into two parts, namely, that part between the master'unit B and said diaphragm and that part between said diaphragm and the brakes A.

The section 25 is in the first mentioned part of the system and is provided with a central bore 23 with which is connected that portion of the pipe 23 which leads from the delivery end of the cylinder It so that said bore constitutes, in effect, apart of said pipe 23. Moreover, the section 25 includes a face '23 which is substantially coextensive with the central,

flexible portion of the diaphragm 21 and which with a chamber 3| with which the bore 33 communicates and into which the diaphragm 21 is flexible under the influence of liquid forced thereagainst in the first mentioned part of the system by pedal actuation of the piston ll of the master unit B.

In the diaphragm 21 is a central opening 33 which afiords communication between the two parts of the system and which is controlled by a suitable check valve 34 which is arranged to open toward the second mentioned part of the system and to close toward the first mentioned part thereof. Associated with the check valve .3! is a light spring 35 which tends constantly to close said valve and to maintain same normally closed.

Normally the foot pedal I3 is held in a raised or retracted position by the spring I! and normally the piston 11 of the masterunit B is held in a retracted position by the spring 23. The first part of the system therefore is devoid of pressure and ofiers no resistance to fiexure of the diaphragm 21 against the face 23 of the housingsection 23. Accordingly, the springs l2 are free to act to contract the brake shoes II and released and thegdiaphragm 21 is maintained against the face 29, and it is understood that under these conditions the second part of the system isfilled with liquid. 1

'uming a normal condition of the syste as recounted, initial depression of the foot pedal It will result in initial movement of the piston II to cover the port 22 and thereby communication between the reservoir 2| and'the end 1 portion of the cylinder IS in advance of the 15 piston I1 will be denied. Liquid thus will be continued depression of the foot pedal I3 with ,continued advance of, the piston I1 will result in the liquid in the first part of the system being The area displaced toward the diaphragm 21. of the diaphragm 21 exposed by the bore 23 is greater than the area of the central opening 33 in said diaphragm. Moreover, since the sec- 25 ond part of the system is filled with liquid when valve 34 but will result in flexure of said diaphragm into the chamber 3!. This, in turn,

' will result in displacement of the liquid in the second part of the system toward the units l3 with the result that the pistons l5, I! of said 35 units will be forced apart and the brakes will be applied. I Upon release of the foot pedal l3, same will be retracted by the spring IS, the piston I! will be retracted by the spring 20, and the brakes 40 will be released by the springs l2, thereby flexing the diaphragm 21 to its normal position against the face 29. I

With wear of the brakes, increased movement of the pistons is, is will be required to apply 5 the brakes and the liquid capacity of the second part of the system thereby will be increased. When such a condition develops and the permissible amount of flexure of the diaphragm 21 does not result in building up a pressure in the second part of the system equal to the pressure developed in the first part of the system-the valve 34 will open and admit liquid from the first part of the system to the second part of the system with the result that the units I3 will be subjected to the pressure developed by the piston II. The brakes thus will be effectively applied and the liquid transferred from the first part of the system to the second part of the system will be trapped in the secondgo part of the system and compensate for the wear 5 mal position. Thus it will be apparent that the unit 0 provides for application of the brakes by a practically -unvarying amount of movement of the foot pedalWluzgardless .of wear of the brakes, and that. any necessity of adjustment to hold said shoes normally in brake-released of the brakes to compensate for wear is elimpositions. With contraction of the brake shoes the pistons II, II of the units l3 are moved towardone another and force liquid in the second part of the system into the chamber 3|,

inated.

In order to insure against trapping of liquid 1 in the space between the diaphragm 21 and the face 23 when said diaphragm is returned to its th b causing the diaphragm 21 to be flexed normal position after having been flexed to apply the brakes, thereby to insure complete and rapid release of the brakes, the section is provided ible part of said diaphragm and extend from said face 29 to the bore 28. In this connection,

.in order to prevent cutting of the diaphragm 21 by the edges of the ducts where they open through the face 29, said face preferably is covered by a sheet 31 of suitable soft material, said sheet having therein openings 38 aiined with the ducts 38.

Without further description it is thought that the features-and advantages of the invention will be readily apparent to those skilled in the art, and it will of course be understood that ,with liquid drain ducts 36 which open through the face 29 near the outer portion of the flex-' and the said face of said wall when the .dia phragml moves toward said face of said wall upon release of the brakes. I

3. In a hydraulic brake system, a brake, a hydraulically operable unit' for applying said brake,

spring means for releasing said brake, a master unit having a closed-circuit liquid connection with said brake-applying unit and including a cylinder and a piston movable therein to exert force on liquid .in the system to effect brake-applying actuation of said brake-applying unit, a

diaphragm in said connection dividing the systern into two parts and arranged to be flexed by changes in the form, proportlon and minor details of construction may be'resorted' to, without departing from the spirit of the invention and scope of the appended claims.

I claim:

liquid forced by said piston and by its flexure to force liquid to the brake-applying unit to actuate the latter to apply the brake, saidmaster unit including a liquid reservoir and means to insure. at all times a supply of liquid from the same to that part of the system between said 1. In a hydraulic brake system, a brake, a hydraulically operable unit for applying said brake, spring means for releasing said brake, a master unit having a closed-circuit liquid connection liquid-filled condition ofthat part of the system between said diaphragm and said master unit, said diaphragm having an opening therein for flow of liquid therethrough, a check valve controlling said opening, said check valve being arranged to open toward said brake-applying,

piston and said diaphragm to maintain said part of the system filled with liquid, said diaphragnr having an opening therein for flow of liquid therethrough, a check valve controlling said=opening, said check valve being arranged to open toward said brake-applying unit and to close toward said master unit whereby liquid may flow from that part of the system between said master unit and said diaphragm to that part of the system between said diaphragm and said brake-applying unit and is prevented from returning from said second mentioned part of the system to said first mentioned part of the system, thus to render the master unit effectiveby an unvarying amount-of movement of the movable element thereof to eifect application of the brake despite wear of the brake.

'4. A- hydrauclic brake system as set forth in I claim 1 including a pair of housing members hetween which the diaphragm is marginally unit and to close toward said master unit whereby liquid may flow from that part of the sys-- tem between said master unit and said di'a phragm to that part of the system between saiddiaphragm and said brake-applying unit and is .prevented from returning from said second mentioned part of the system to said first mentioned part of the system, thus to render the master unit effective by an unvarying amount of movement of the movable element thereof to effect. application of the brake despite wear of the brake.

2. A hydraulic brakesystem as set forth in claim 1 including a wallto limit flexure of the diaphragm toward the master unit, said wall being substantially coextensive with the flexible portion .of said diaphragm and having liquid drain openings therein leading from portions of the face of said wall engaged by marginal portions of the diaphragm to the first mentioned part of the system to insure complete and rapid drainage of liquid'from between said diaphragm clamped, one of said members having a chamber into which said diaphragm is flexible, the other of said members having a wall substantially coextensive with the flexible portion of said diaphragm and serving to limit flexure of said diaphragm toward the master unit.

,5. A hydraulic brake system as set forth in claim 1 including a wall to limit flexure of the diaphragm toward the master unit, said wall being substantially coextensive with the flexible portion of said diaphragm and having liquid drain openings therein leading from portions of the face of said wall engaged by marginal portions of the diaphragm to the first mentioned part of the system to insure complete and rapid drainage of liquid from between said diaphragm and the said face of said wall when the diaphragm moves toward said face of said well upon release 10f the brakes, and a pad disposed against said face of saidwall to'prevent cutting of the diaphragm by the edges of said openings.

' JAY w. DUDLEY. 

